修复优卡特机型非当前机型崩溃的问题

app/src/main/java/android_serialport_api/SerialPort.java

 package android_serialport_api;
 
-import android.util.Log;
-
 import java.io.File;
 import java.io.FileDescriptor;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
-import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 
@@ -30,11 +27,11 @@ public class SerialPort {
                 String cmd = "chmod 666 " + device.getAbsolutePath() + "\n" + "exit\n";
                 su.getOutputStream().write(cmd.getBytes());
                 if ((su.waitFor() != 0) || !device.canRead() || !device.canWrite()) {
-                    throw new SecurityException();
+                    return null;
                 }
             } catch (Exception e) {
                 e.printStackTrace();
-                throw new SecurityException();
+                return null;
             }
         }